The thyristor converter with its advantages of high efficiency, good energy saving effect, fine controlling characteristics and long life, etc., is extensively used in the fields of electric power, metallurgy, machinery, chemical industry and communications, etc., but its development and utilization are far from reaching the desired extent. The main reason is the complexity of the thyristor converter system; in order to set up such a system, work is massive and extremely complicated, and nonprofessional technicians are incompetent for the job. Therefore, its application is greatly obstructed. If the complex system may be simplified to an assembly module, employment of the thyristor will become very simple, and application of thyristor will also be rapidly extended.
The thyristor converter chiefly consists of the two parts: one part is the main circuit system of the thyristor, its mounting and wiring can be achieved according to various needs; another part is the trigger system, i.e., to trigger the gate electrode of the main circuit thyristor via controlled phase angle variation, thereby to control the voltage and current of the main circuit load, and realize the purpose of conversion. For many years, no major variations have occurred in the operational principle of the trigger system, the operational principle of the products currently on sale in the market (such as the products of the Beijing No.2 Semiconductor Devices Factory and the Xi'an Keyi Electronics Co., Ltd.) remains essentially the same as what is taught in the textbook ((Electric Power Electronic Technology)) (Edited by Ding Daohong, Aeronautical Industry Press, June 1992). These conventional trigger systems comprise a synchronous signal sampling circuit, an integrating circuit, a comparator, and an output circuit. Such system is not only difficult to be installed, but also requires that, because of the three-phase balance problem of the synchronous power signal input transformer, .DELTA.connection must be employed, which resulted in that normal work has to be performed on distinguishing phase sequence of the whole system. When any variation in the phase sequence of external power source occurs, the whole system will not be able to operate normally. Since the thyristor may generate or be disturbed by the external interference, and the synchronous signal is achieved by the synchrotrans, while the transformer per se does not possess antiinterference performance, this trigger system is deficient in antiinterference performance too. As the synchrotrans has requirements for rated voltage, consequently the system can only operate at rated voltage and its adaptable range of voltages is narrow. Especially for the trigger circuit of large power silicon controlled rectifier (SCR), its trigger circuit, synchronous sampling transformer and various segmental circuits are very large in size, and inconvenient to use. In addition, the structure of the trigger pulse output circuit is irrational, high in power consumption, big in size, and expensive in cost.
The main circuit and the trigger circuit of the thyristor should be mounted, phased, wired, and adjusted by the user. To achieve this work, the user should also be an experienced technician.